1. Field of the Invention
The present invention relates to a lens driving device employed in an optical device, and more particularly, to a lens driving device which is simplified in a driving mechanism to achieve a smaller size, minimized in loss of a driving force for driving a lens and ensures more accurate and stable movement of the lens.
2. Description of the Related Art
In general, an optical apparatus includes a lens driving device for driving a lens using a cam structure, a screw or a piezoelectric element. The lens driving device employs a motor or the piezoelectric element to generate a driving force and the cam structure or the screw to transmit the driving force.
Therefore, the lens driving device drives the lens to change a relative distance of the lens, thereby performing zooming or focusing.
U.S. Pat. No. 5,768,038 discloses a device for moving a lens including a lens frame, a signal generator, a piezoelectric vibrator, a supporter, a pressure surface and a pressure member. The guiding member guides a lens frame. The signal generator generates an electrical signal. The piezoelectric vibrator moves the lens frame along the guiding member by vibration according to the electrical signal. The supporter supports the piezoelectric vibrator. The pressure surface is in pressure contact with the piezoelectric vibrator. The pressure member brings the piezoelectric vibrator into pressure contact with the pressure surface.
However, this conventional device requires the guiding member to be additionally assembled so that the lens frame is moved in an optical axis direction. This complicates an assembling structure and a process, and hinders miniaturization of the product.
Moreover, U.S. Pat. No. 6,215,605 discloses a driving device. In the driving device, piezoelectric devices are fixed to a base block and a driving force is transferred to driving rods. Then, a lens is moved by a pressure generated from a slide part, an inertial force of a lens frame and acceleration effects. The lens frame is transferred along with the driving rods according to a waveform of an input voltage or performs slidable relative motion, thereby enabling the driving device to reciprocally move the lens.
However, in this conventional device, the driving rods are fixed so that a length of barrel cannot be changed. This accordingly is an impediment to reduction in size. Also, a driving signal of the device is an asymmetrical wave signal, not a sine wave signal, thereby complicating a driving circuit.
Therefore, there is a need for a lens driving device which can be mounted in a small volume, controlled precisely due to high driving resolution, while operating with a small driving power and achieving a sufficient driving distance.